CORE B- PATHOLOGY The Pathology Core is an important part of the Seattle hematopoietic stem cell transplant program, which is supported by the Adult Leukemia Center (ALC) grant and is located at the Fred Hutchinson Cancer Research Center. The core is a highly integrated group of physicians and laboratory technicians representing four disciplines. These are pathology, flow cytometry and cell sorting, polymerase chain reaction detection of malignant cell markers, and cytogenetics. The mission of the core is to provide support necessary for accomplishing the research goals of the transplant program. Our major focus is the detection and identification of malignant cells, even when these are present in very small numbers. This information is critical for successful treatment of patients with cancer. In addition, the core provides very important information about how well the donor cells are populating the bone marrow and producing normal red and white blood cells as well as platelets for release into the blood stream. We also have very sensitive methods for quickly detecting infection and can evaluate tissue samples for graft-versus-host disease (GVHD) as well as possible damage from treatment drugs or irradiation. Anatomic pathology uses standard methods in addition to immunohistochemistry and in situ hybridization on tissue sections to diagnose infection, GVHD, relapse of malignancy or development of second tumors, and the presence and extent of chimerism(the simultaneous presence of host and donor cells). Molecular cytogenetics uses fluorescence in situ hybridization (FISH) to recognize chimerism and tumors. Molecular pathology uses PCR methods to detect minimal residual disease. Multiparameter flow cytometry with sorting provides a highly sensitive method for detecting small numbers of abnormal cells and separating them for studies carried out by other members of the core. Relevance to Public Health:These methods provide key support for virtually all projects and core components of the ALC transplant program. Through these efforts, we are developing improved methods for returning cancer patients to full health and normal lives. At the same time, we are identifying ways in which the body defends itself, and this knowledge can be helpful in attaining the goal of cancer prevention.